The array can be shown as 5 groups of 3 showing that 5 x 3 = 15. Or it could be shown as 3 groups of 5 showing that 3 x 5 = 15. This demonstrates that multiplication is commutative. Image caption, ...

Knowing your multiplication facts is very useful, but what happens when the numbers you are multiplying are greater than those in your multiplication tables? You will need to calculate using a column ...